Integrated multi-mode mammography/tomosynthesis X-ray system and method

ABSTRACT

A system for multi-mode breast x-ray imaging which comprises a compression arm assembly for compressing and immobilizing a breast for x-ray imaging, an x-ray tube assembly, and an x-ray image receptor is provided. The system is configured for a plurality of imaging protocols and modes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Rule 1.53(b) continuation of application Ser. No.11/791,601 (now allowed) filed Feb. 22, 2008 now U.S. Pat. No. 7,869,563as a U.S. national phase application under 35 U.S.C. 371 ofInternational Application No. PCT/US2005/042613, filed Nov. 23, 2005,which claims the benefit of U.S. Provisional application No. 60/631,296filed Nov. 26, 2004, and also is related to application Ser. No.12/397,013 filed Mar. 3, 2009 (which also claims the benefit ofapplication Ser. No. 11/791,601). The entire contents of each of theabove-identified applications are incorporated by reference herein.

FIELD

This patent specification pertains to x-ray mammography and, morespecifically, to an integrated system for selectively carrying out x-raymammography and/or tomosynthesis imaging and a method of using such asystem.

BACKGROUND

X-ray mammography has long been a screening modality for breast cancerand other lesions, and also has been relied on for diagnostic and otherpurposes. For many years, the breast image was recorded on x-ray filmbut more recently digital x-ray image receptors have come into use, asin the Selenia™ mammography system available from Hologic Inc. ofBedford, Mass. and its division Lorad Corporation of Danbury, Conn. Formammograms, a cone-shaped or pyramid-shaped x-ray beam passes throughthe compressed breast and forms a two-dimensional projection image. Anyone of a number of orientations can be used, such as cranial-caudal (CC)or MLO (mediolateral-oblique) orientation. More recently, breast x-raytomosynthesis has been proposed. The technology typically involvestaking two-dimensional (2D) projection images of the immobilized breastat each of a number of angles of the x-ray beam relative to the breastand processing the resulting x-ray measurements to reconstruct images ofbreast slices that typically are in planes transverse to the x-ray beamaxis, such as parallel to the image plane of a mammogram of the samebreast. The range of angles is substantially less than in computerizedtomography, i.e. substantially less than 180°, e.g. ±15°. Tomosynthesistechnology is described in U.S. patent application Ser. No. 10/723,486filed Nov. 26, 2003; a prototype of a unit with at least some of thedescribed features was shown at the 2003 Radiological Society of NorthAmerica meeting in Chicago, Ill. Additional prototypes are in clinicaltesting in this country as of the filing of this patent specification.Other approaches to tomosynthesis also have been proposed: see, e.g.,U.S. Pat. Nos. 4,496,557, 5,051,904, 5,359,637, 6,289,235, and6,647,092, published U.S. Patent Applications Nos. 2001/0038861,2004/066882, 2004/0066884, and 2004/0066904, and Digital ClinicalReports, Tomosynthesis (GE Brochure 98-5493, November 98). How toreconstruct tomosynthesis images is discussed in DG Grant,“Tomosynthesis: a three-dimensional imaging technique”, IEEE Trans.Biomed. Engineering, Vol BME-19, #1, (January 1972), pp 20-28. See,also, U.S. Provisional Application Ser. No. 60/628,516, filed Nov. 15,2004, and entitled “Matching geometry generation and display ofmammograms and tomosynthesis images”. Mammography systems can also beused in interventional procedures, such as biopsy, by adding a biopsystation (for example, the StereoLoc II™ Upright Stereotactic BreastBiopsy System, which is available from Hologic, Inc.). The patents,applications, brochures, and article cited above are hereby incorporatedby reference in this patent specification as though fully set forthherein.

In clinical use, it can be desirable for a number of reasons to assessboth tomosynthesis images and conventional mammograms of the patient'sbreasts. For example, the decades of conventional mammograms haveenabled medical professionals to develop valuable interpretationexpertise. Mammograms may offer good visualization ofmicrocalcifications, and can offer higher spatial resolution comparedwith tomosynthesis. Tomosynthesis images may have different desirablecharacteristics—e.g., they may offer better visualization of structuresthat can be obscured by overlying or underlying tissue in a conventionalmammogram.

While the existing and proposed systems for x-ray mammography andtomosynthesis offer many advantages, it is believed that a need stillexists for further improvements to make mammography/tomosynthesis moreuseful, and that it is particularly desirable to make it possible to usethe same system in different modes of operation and thereby reduceacquisition and operating costs and provide greater clinical value andconvenience.

SUMMARY

This patent specification describes examples of systems and methods formulti-mode breast x-ray imaging. A single system carries out breastimaging in modes that include standard mammography, diagnosticmammography, dynamic imaging such as with a contrast agent and atdifferent x-ray energies, tomosynthesis imaging, combined standard andtomosynthesis imaging during a single breast compression, needlelocalization, and stereotactic imaging with a biopsy station mounted tothe system.

In an example of a system using the teachings of this patentspecification, a compression arm assembly for compressing andimmobilizing the breast for x-ray imaging, an x-ray tube assembly, andan x-ray image receptor can be angled relative to each other fordifferent imaging protocols and modes. They can be independently rotatedand synchronized as needed, or can be mechanically linked forappropriate synchronized rotation. A patient shield can be mounted tothe compression arm assembly to provide a mechanical interlock againstpatient contact with the rotating x-ray tube assembly. A fullyretractable anti-scatter grid can be used that can cover the imagingarea of the x-ray receptor in some modes but be retracted completelyoutside the imaging area for other modes.

The exemplary system further includes a breast compression paddle thatis laterally movable, under manual control or when motorized andoperating under software control. The compression paddle can shiftautomatically depending on the view to be acquired. For example, thepaddle can be centered on the x-ray receptor for a CC view, shifted toone lateral side of the receptor for an MLO view of one breast and tothe other lateral side of the receptor for an MLO view of the otherbreast. The paddle can be automatically recognized by the system whenmounted so that the shifts can be adjusted to the type of paddle.

The compression paddle can be easily removable from a support that has amechanism for laterally moving the paddle and for allowing the paddle totilt for better conformance with the breast for selected image modes butlocking the paddle against tilt for other modes. With the movementmechanism in the support and not integral with the paddle, the paddlecan be simple and inexpensive, and easy to mount to and remove from thesupport. A number of relatively inexpensive paddles of different sizesand shapes can be provided and conveniently interchanged to suitdifferent procedures and patients.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a gantry and an acquisition workstationin accordance with an example of the disclosed system.

FIG. 2 is an enlarged view of a portion of the system of FIG. 1, with atube arm assembly in a rotated position.

FIG. 3 is a front elevation of the apparatus of FIG. 2.

FIG. 4 is a side view of a gantry with a biopsy station and a spacer,with schematic illustration of other mechanisms.

FIG. 5 is an enlarged view of a portion of FIG. 1.

FIG. 6 is a block diagram of the disclosed system when connected toother systems.

FIG. 7 is a flow chart illustrating a general work flow for thedisclosed system.

FIG. 8 is a flow chart illustrating one of several examples of work flowfor a standard mammography mode.

FIG. 9 is a flow chart illustrating one of several examples of work flowfor an image detector subsystem in the standard mammography mode.

FIG. 10 is a perspective view of the structure of FIG. 4.

FIG. 11 is similar to FIG. 2 but shows a tube arm assembly angleddifferently.

FIG. 12 is a front elevation of the structure of FIG. 11.

FIG. 13 is a flow chart illustrating one of several examples of workflow for a tomosynthesis mode.

FIG. 14 is a flow chart illustrating one of several examples of workflow for an image detector subsystem in the tomosynthesis mode.

FIG. 15 is a flow chart illustrating one of several examples of workflow for a combination mode.

FIG. 16 is a flow chart illustrating one of several examples of workflow for an image detector subsystem in the combination mode.

FIG. 17 is an enlarged side view of a structure for removably mounting abreast compression paddle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In describing examples and preferred embodiments illustrated in thedrawings, specific terminology is employed for the sake of clarity.However, the disclosure of this patent specification is not intended tobe limited to the specific terminology so selected and it is to beunderstood that each specific element includes all technical equivalentsthat operate in a similar manner.

FIGS. 1-6 illustrate a non-limiting example of a multi-modemammography/tomosynthesis system comprising a gantry 100 and a dataacquisition work-station 102. Gantry 100 includes a housing 104supporting a tube arm assembly 106 rotatably mounted thereon to pivotabout a horizontal axis 402 (FIG. 4) and carrying an x-ray tube assembly108. X-ray tube assembly 108 includes (1) an x-ray tube generating x-rayenergy in a selected range, such as 20-50 kV, at mAs such as in therange 3-400 mAs, with focal spots such as a nominal size 0.3 mm largespot and nominal size 0.1 mm small spot (2) supports for multiplefilters such as molybdenum, rhodium, aluminum, copper, and tin filters,and (3) an adjustable collimation assembly selectively collimating thex-ray beam from the focal spot in a range such as from 7×8 cm to 24×29when measured at the image plane of an x-ray image receptor included inthe system, at a maximum source-image distance such as 75 cm. Alsomounted on housing 104, for rotation about the same axis 402, is acompression arm assembly 110 that comprises a compression plate 122 anda receptor housing 114 having an upper surface 116 serving as a breastplate and enclosing a detector subsystem system 117 comprising a flatpanel x-ray receptor 502 (FIG. 5), a retractable anti-scatter grid 504and a mechanism 506 for driving and retracting anti-scatter grid 504.Housing 104 also encloses the following components schematicallyillustrated in FIG. 4: a vertical travel assembly 404 for moving tubearm assembly 106 and compression arm assembly 110 up and down toaccommodate a particular patient or imaging position, a tube armassembly rotation mechanism 406 to rotate tube arm assembly 106 aboutaxis 402 for different imaging positions, a detector subsystem rotationmechanism 408 for rotating components of detector subsystem 117 (such asx-ray receptor 502) about axis 402 to accommodate different operationmodes, and couple/uncouple mechanism 410 to selectively couple oruncouple tube arm assembly 106 and compression arm assembly 110 to andfrom each other, and tube arm assembly 106 and detector subsystem 117 toand from each other. Housing 104 also encloses suitable motors andelectrical and mechanical components and connections to implement thefunctions discussed here. A patient shield 200, schematicallyillustrated in FIG. 2, can be secured to compression arm assembly 110 toprovide a mechanical interlock against patient contact with the rotatingx-ray tube arm assembly 106. Work-station 102 comprises componentssimilar to those in the Selenia™ mammography system, including a displayscreen (typically a flat panel display that may include touch-screenfunctionality), user interface devices such as a keyboard, possibly atouch-screen, and a mouse or trackball, and various switches andindicator lights and/or displays. Work-station 102 also includescomputer facilities similar to those of the Selenia™ system (but adaptedthrough hardware, firmware and software differences) for controllinggantry 100 and for processing, storing and displaying data received fromgantry 100. A power generation facility for x-ray tube assembly 108 maybe included in housing 104 or in work-station 102. A power source 118powers work-station 102. Gantry 100 and work-station 102 exchange dataand controls over a schematically illustrated connection 120.

As illustrated in FIG. 6, additional storage facilities 602 can beconnected to work-station 102, such as one or more optical disc drivesfor storing information such as images and/or for providing informationto work-station 102 such as previously obtained images and software, ora local printer (not shown). In addition, the disclosed system can beconnected to a hospital or local area or other network 604, and throughthe network to other systems such as a soft copy workstation 606, a CAD(Computer Aided Detection) station 608 for computer-processingmammography and/or tomosynthesis images to identify likelyabnormalities, an image printer 610 for printing images, a technologistworkstation 612, other imaging systems 614 such as other mammographysystems or systems for other modalities for exchange of images and/orother information, and to a PACS (Picture Archiving) systems 616 forarchiving images and other information and/or retrieving images andother information.

The illustrated system has several modes of operation. An example oftypical workflow generally applicable for each mode is illustrated inFIG. 7, and several examples of operational modes are discussed below.Of course, this is only one example and workflow steps may be arrangeddifferently. In all modes, the operator can perform x-ray exposure usingmanual setting of technic factors such as mA and mSec, or can use anautomatic exposure control as known in the art to set the exposure time,kV and filter modes for an image, for example by using a short,low-x-ray dose pre-exposure. Work-station 102 is set up to record theexposure technic information and associate it with the breast image forlater review. The steps illustrated in FIG. 7 are:

701, in which a user/technologist logs in:

702, in which patient demographics are entered:

703, which comprises review of previous examination;

704, in which the study is selected;

705, in which the technique is set up or an auto-setup of technique isperformed;

706, in which the patient is positioned;

707, in which the technique is verified and/or modified:

708, in which the technique is confirmed;

710, in which the exposure button is pushed;

710, in which the technologist reviews the preview image, such as forparameters indicated in the box to the right;

711, in which a decision is made whether to accept the image:

712, in which the image is rejected if step 711 has not accepted theimage;

713, in which the image accepted in step 712 is saved (sent to theoutput device);

714, in which a test is made whether after step 714 (or 713) the studyis complete and, if not, the process returns to step 705. and

715, which closes the procedure if step 715 determines that the study iscomplete.

In standard mammography mode, typically used for screening mammography,tube arm assembly 106 and compression arm assembly 110 are coupled andlocked together by 410 in a relative position such as seen in FIG. 1,such that an x-ray beam from x-ray tube assembly 108 illuminates x-rayreceptor 502 when the patient's breast is compressed by compressiondevice 112. In this mode, the system operates in a manner similar tosaid Selenia™ system to take a mammogram. Vertical travel assembly 404and tube arm rotation mechanism 406 can make vertical adjustments toaccommodate a patient, and can rotate tube arm assembly 106 andcompression arm assembly 110 together as a unit about axis 402 fordifferent image orientations such as for CC and for MLO images. Forexample, tube arm assembly 106 and compression arm assembly 110 canrotate between)(−195°) and (+150°) about axis 402. As in the Selenia™system, compression device 112 includes a compression paddle 122 thatcan move laterally, in a direction along the chest wall of a patient, toadjust for different imaging orientations. However, as described furtherbelow, the mechanism for supporting and moving compression paddle 122 isdifferent. Typically, anti-scatter grid 504 is over x-ray receptor 502in the standard mammography mode to reduce the effect of x-ray scatter.FIG. 8 illustrates a typical workflow for an exposure in standardmammography mode, and FIG. 9 illustrates an example of the operation ofdetector subsystem 117 in standard mammography. Of course, these areonly examples; other workflow steps or orders of steps can be usedinstead. The steps illustrated in FIG. 8 are:

801, in which the examination is setup and the patient is positioned;

802, in which the expose button is pressed;

803, in which the system is ready for exposure and x-ray begins;

804, in which exposure takes place in an x-ray window;

805, in which a decision is made whether to view a preview image;

806, in which the preview image is viewed if the decision at step 805was to do so;

807, in which a test is made to determine whether the study is complete,and the process is directed to repeating step 801 is the study is notcomplete;

808, in which a full image is captured, whether or not previewed; and

809, in which the procedure is closed if the test at step 807 determinesthat the study is complete; and

810, in which the captured image is saved;

The steps illustrated in FIG. 9 are:

901, in which the detector receives an image capture request;

902, in which the detector is ready for image capture;

903, in which an exposure window is open;

903, in which the detector is read out;

904, in which the image data is available to the host; and

906, in which a test is made whether the host is done with reading thedata and, if the host is done reading the data, returns the process tostep 901 but if the host is not done with reading the data, recyclesthrough step 906 until the test answer is that the host is done readingthe data.

In a diagnostic mode, the patient's breast can be spaced from uppersurface 116, for example by an x-ray translucent spacer 1002 (FIG. 10),with the system otherwise similar to FIG. 1, for a magnification of upto 1.8, for example. In this mode, as in standard mammography, tube armassembly 106 and compression arm assembly 110 are locked to each otherand can move up or down and rotate about axis 402 for different imageorientation. A different spacer 1002 can be used for a different degreeof magnification. Also, differently shaped or dimensioned compressionpaddles 122 can be used for different breast compression effects. Thex-ray tube in x-ray tube assembly 108 can be set to a smaller focal spotsize to improve a diagnostic image. In this mode, anti-scatter grid 504typically is retracted when magnification is used such that grid 504 iscompletely out of the image. The user can elect not to use a spacer 1002in diagnostic imaging, in which case anti-scatter grid 504 can be usedover the entire image.

In a dynamic imaging mode, a number of breast images are taken while thepatient's breast remains compressed. In one technique, an agent such asiodine is injected into the patient and after a suitable waiting timesuch as about one minute for a maximum uptake, two images breast aretaken in rapid succession, for example one at an x-ray energy just abovethe K-edge of iodine and one at an energy just below the K-edge.Alternatively, a succession of breast images can be taken at a singlex-ray energy band or bands just above and below the K-edge, or atanother x-ray energy range, to track the uptake of agent over time.Another technique adds taking a baseline breast image before or soonafter injecting the agent and using it together with later breast imagesto generate subtraction images that provide better visualization ofanatomy that may be of interest. Still another dynamic imaging modetechnique comprises injecting a contrast agent and taking a successionof images over a period such as 5-7 minutes, for example one image everyminute, and processing the image data to generate for each pixel, or atleast for each pixel of interest, a histogram of the change in the pixelvalue, to thereby use the manner in which pixel values change todifferential abnormal tissue. For this mode, work-station 102 can storepreset data that commands gantry 100 and work-station 102 to take adesired sequence of images for the dynamic mode technique selected bythe operator, such that the command data sets the appropriate parameterssuch as x-ray energy, dose, timing of images, etc. Alternatively, suchprocessing to assess changes in pixel values can be done for a region ofinterest rather than over individual pixels, to produce information suchas a measure of changes in the average pixel values in the region ofinterest.

In tomosynthesis mode, tube arm assembly 106 and compression armassembly 110 are decoupled by unit 410 such that compression armassembly 110 stays in one position, compressing the patient's breast,while tube arm assembly 106 rotates about axis 402, for example betweenthe position illustrated in FIG. 2 to that illustrated in FIG. 11, or±15° relative to compression arm assembly 110. Tomosynthesis can becarried out for different image orientations, so that compression armassembly 110 can be rotated about axis 402 (alone or together withassembly 106) for a desired image orientation and locked in place, andthen tube arm assembly 106 can be rotated relative to that position ofcompression arm assembly 110 for tomosynthesis imaging over ±15° or someother desired angular range. In one example, 11 images are taken duringan angular sweep of tube arm assembly 106, one every approximately 3° .However, a different number of images can be taken, for example up to 21during a single sweep. For tomosynthesis images, the x-ray tube in x-raytube assembly 108 continuously rotates and the x-ray tube is pulsed foreach image, for example, for x-ray energy pulses each lastingapproximately 100 mSec, although pulses of different duration can beselected. Alternatively, the rotational motion can stop for taking eachimage, or continuous motion without pulsing can be used (and the timingof data measurements relied on to define pixel values). As seen in FIGS.2, 3, 5, 11 and 12, in this mode mechanism 506 fully retractsanti-scatter grid 504 away from x-ray receptor 502 so grid 504 is out ofthe image. Also as seen in these Figs., while the breast remainsimmobilized in compression arm assembly 110 during the angular sweep oftube arm assembly 106, x-ray receptor 502 rocks within receptor housing114. In this rocking motion, controlled by unit 408 (FIG. 4), a linenormal to the image face of x-ray receptor 502 may keep pointing to thefocal spot of the x-ray tube in x-ray tube assembly 108. Alternatively,the rotation of tube arm assembly 106 and rocking of x-ray receptor 502can be through different angles; for example, tube arm assembly 106 canrotate through 15° while x-ray receptor 502 rocks through 5° , i.e. therocking angle can be an amount one-third that of assembly 108.Synchronous rotation of tube arm assembly 106 and rocking of x-rayreceptor 502 can be achieved by controlling separate motors for each or,alternatively, through using a motor to drive tube arm assembly 106 anda mechanical coupling between the rotation of tube arm assembly 106 androcking of x-ray receptor 502. Image data can be obtained and processedinto tomosynthesis images for display and/or storage as described in thematerial incorporated by reference, for example in U.S. patentapplication Ser. No. 10/723,486, now U.S. Pat. No. 7,831.296, or in U.SProvisional Application No. 60/628,516, filed Nov. 15, 2004. FIG. 13illustrates a typical workflow for tomosynthesis mode operation, andFIG. 14 illustrates an example of the operation of detector subsystem117 in that mode. Again, these are only examples, and other steps ororders of steps can be used instead. The steps illustrated in FIG. 13are:

1301, in which the examination is setup and the patient is positioned;

1302, in which the expose button is pressed;

1303, in which the system is ready for exposure and x-ray begins;

1304, in which exposure takes place in an x-ray window, and is repeatedas indicated in the box to the right;

1305 in which a test is made whether to view a projection preview image

1306, in which the preview image is viewed if the decision at step 1306was to do so;

1307, in which a test is made to determine whether the study iscomplete, and the process is directed to repeating step 1301 is thestudy is not complete;

1308, in which reconstruction and full image capture take place, whetheror not the preview image was viewed in step 1307;

1309, in which the procedure is closed if the test at step 1307determines that the study is complete; and

1310, in which the image from step 1308.

The steps illustrated in FIG. 14 are:

1401, in which the detector receives a tomo capture request;

1402, in which the detector is ready for capture;

1403, in which an exposure window is open;

1404, in which the detector is read out;

1404, in which the expose/readout cycle is repeated the expose/readoutcycle is repeated as indicated in the box to the right; and

1405, in which all image frames are available to the host; and

1406, in which a test is made whether the host is done with reading thedata and, if so, the process is returned to step 1401 but if not, step1407 recycles until the test answer is that the host is done reading thedata.

In a combination mode, during a single compression of the patient'sbreast the system takes a conventional mammogram and tomosynthesisimages. In this mode, while the breast remains compressed in compressionarm assembly 110, (1) tube arm assembly 106 sweeps and x-ray receptor502 rocks, each through an appropriate angle, and exposures are takenfor tomosynthesis images, and (2) a standard mammogram is taken. Thestandard mammogram can be taken at a 0.degree. relative angle betweentube arm assembly 106 and a normal to the imaging plane of x-rayreceptor 502, and can be taken before or after the tomosynthesis imagesare taken or between the taking of two successive tomosynthesis images.Typically, each tomosynthesis image utilizes substantially lower x-raydose than the standard mammogram. For example, the total x-ray dosagefor tomosynthesis imaging in one sweep of tube arm assembly 106 can beapproximately the same as that for a single standard mammogram, or up toapproximately three times that dosage. The relationship between the twodosages can be user-selected. FIG. 15 illustrates an example of workflowfor the combination mode, and FIG. 16 illustrates an example of theoperation of detector subsystem 117 in that mode. The steps illustratedin FIG. 15 are:

1501, in which the examination is setup and the patient is positioned;

1502, in which the expose button is pressed;

1503, in which the system is ready for exposure and the scan starts;

1504, in which tomo exposure takes place in an x-ray window andprojection exposures are repeated as indicated in the box to the right;

1505, in which a test is made whether to view a projection preview image

1506, in which the preview image is viewed if the decision at step 1506was to do so;

1507, in which the C-arm is auto-positioned for standard scan, whetheror not step 1505 determined that a preview image should be viewed;

1508, in which reconstruction is performed;

1509, in which a standard exposure is performed (x-ray begins);

1510, in which image preview takes place (tomo and standard);

1511, in which a test is made to determine whether the study iscomplete, and the process is directed to repeating step 1501 is thestudy is not complete;

1512, in which complete reconstruction and image capture take place; and

1513, in which the procedure is closed if the test at step 1511determines that the study is complete.

The steps illustrated in FIG. 16 are:

1601, in which the detector receives a combo capture request;

1602, in which a tomosynthesis image cycle is performed;

1603, in which a standard image cycle is performed; and

1604, in which a test is made to determine if the host is done withreading data and, if so, the process is returned to step 1601 but ifnot, the process cycles through step 1604 until the test shows that thehost is done with reading data.

Again, these are examples, and different steps or orders of steps can beused instead. For example, a preferred approach may be to take thestandard mammogram first, then move arm 106 to one end of its rotationalrange for tomosynthesis and take the tomosynthesis images. The order inwhich the two types of images are taken may be optimized such that theoverall imaging time is minimized, and an order that achieves suchminimization can be the preferred order. The exposure (tube current mA,tube voltage kVp, and exposure length msec) techniques for the standardmammogram and the tomosynthesis exposures can be set manually, or byusing automatic methods. If the standard mammogram is taken first, itsexposure techniques can be used to set an optimal technique for thesubsequent tomosynthesis images, and vice versa. The exposure techniquecan be modified dynamically, if the software senses that the signalreaching the image receptor is either too low or too high and adjustsubsequent exposures as needed.

In a stereotactic mode, during a single compression of the patient'sbreast at least two images are taken, for example one at (+15)° angleand one at (−15°) angle of tube arm assembly 106 relative to compressionarm assembly 110, although other angles can be used and more images canbe taken. X-ray receptor 502 can remain in place for this procedure, orcan be rocked through a selected angle, for example through an anglesufficient to maintain the same orientation of the imaging surface ofreceptor 502 relative to tube arm assembly 106. A spacer 1002 can beused for magnification. If x-ray receptor 502 remains in place despiterotation of arm 106, or if spacer 1002 is used, anti-scatter grid 504 isfully retracted; if x-ray receptor 502 maintains its orientationrelative to tube arm assembly 106 and no spacer 1002 is used,anti-scatter grid 504 need not be retracted. As is known in the art, thetwo or more images can be used to identify the location of a lesion, sothat needle biopsy can be used, for example with an upright needlebiopsy station 412 (FIG. 4) in a manner similar to that used with thecommercially available Selenia™ system and StereoLoc II™. A compressionpaddle 122 appropriate for needle biopsy typically is used when takingthe stereotactic images. Alternatively, some or all of the images takenin the tomosynthesis mode and/or in the combined mode can be used toidentify the location of a lesion for biopsy, in which case acompression paddle 122 appropriate for the purpose typically is usedwhen taking the images.

In needle localization mode, x-ray images can be taken after a biopsy orother needle is inserted into the compressed breast. For this purpose,imaging such as in the stereotactic mode, the tomosynthesis mode, or thecombined mode can be used.

In the disclosed system, compression paddle 122 is movable laterally, asgenerally described in U.S. Patent Application Publication No.2005/0063509 A1, hereby incorporated by reference herein. In addition,compression paddle 122 can pivot about an axis along the patient's chestwall to conform the breast shape in certain procedures, as discussed insaid U.S. Pat. No. 5,706,327. However, in the system of this patentspecification compression paddle 122 is mounted differently and moves ina different manner.

As illustrated in FIGS. 5 and 17, compression paddle 122 is removablymounted to a support 510 that moves up and down compression arm assembly110 as needed for breast compression. To mount compression paddle 122onto 510, a projection compression paddle 122 a of the paddle engages aprojection 510 a of the support, and a projection 122 b of the paddlelatches onto projection 510 b of the support. Projection 510 a isspring-loaded, such as by a spring schematically illustrated at 510 c toallow for pivoting compression paddle 122 about an axis where it latchesonto 510, as illustrated by arrow A, for better conformance with thecompressed breast in some imaging protocols. Other imaging protocols mayrequire compression paddle 122 not to pivot, in which case projection510 a is locked in place by a locking mechanism in 510 (not shown) tokeep compression paddle 122 in place relative to support 510. Thelocking mechanism can be manually set to a lock position, and manuallyunlocked by the operator. Alternatively, the locking mechanism can becontrolled through an operator input at gantry 100 or work-station 102.A sensing mechanism can be included to sense whether compression paddle122 is locked against pivoting, to provide information that work-station102 can use for setting imaging protocols such as for automated breastcompression and automated exposure methods. Two knobs 510 d, one on eachlateral side of support 510, can be manually rotated to move projection510 b and thus compression paddle 122 laterally such that it compress abreast that is not centered laterally on upper surface 116, for examplefor MLO imaging. Each knob 510 d can operate a mechanism such as anendless screw rotating in a nut secured to projection 510 b.Alternatively, or in addition, projection 510 b and thus compressionpaddle 122 can be driven laterally by a motor, under control of operatorswitches or other interface at gantry 100 or at work-station 102, orautomatically positioned laterally under computer control.

Importantly, compression paddle 122 is driven for lateral movement bycomponents that are a part of support 510. Thus, compression paddle 122can be a simple structure, and can even be disposable, with a new oneused for each patient or for only a few patients. This can simplify andreduce the cost of using the system, because an imaging facility usuallystocks a number of different paddles for different purposes. If thelateral movement mechanism is integral with a compression paddle, thepaddle assembly is considerably larger, heavier and more expensive. Butwith a compression paddle 122 that relies for lateral movement onsupport 510, and is easily mounted by hand and without tools to support510, by sliding compression paddle 122 a into projection 510 a andlatching projection paddle 122 b onto projection 510 b, and is easilyremoved by reversing the process, the expense of keeping a number ofdifferent compression paddles in stock or replacing paddles with newones is greatly reduced, as are the time and convenience when changingfrom one type of compression paddle to another. Compression paddle 122can include a bar code that is automatically read by a bar code readerin support 510, to keep work-station 102 informed of the paddlecurrently mounted to support 510, for use in automating imagingprotocols. For example, the bar code information can be checked toensure through computer processing that the type of paddle that iscurrently mounted on support 510 matches the imaging that will becommanded, and the information from the sensor for whether compressionpaddle 122 is locked in non-tilting mode can be used to automaticallymake adjustments for compression height to ensure accurate automaticx-ray exposure operation. Further, the bar code information identifyingthe paddle can be used to automatically set collimation in x-ray tubeassembly 108 so that the x-ray beam matches the size and shape of thecurrently installed compression paddle 122.

The above specific examples and embodiments are illustrative, and manyvariations can be introduced on these examples and embodiments withoutdeparting from the spirit of the disclosure or from the scope of theappended claims. For example, elements and/or features of differentillustrative embodiments may be combined with each other and/orsubstituted for each other within the scope of this disclosure andappended claims.

This application claims the benefit of U.S. provisional application Ser.No. 60/631,296, filed Nov. 26, 2004 and entitled “INTEGRATED MULTI-MODEMAMMOGRAPHY/TOMOSYNTHESIS X-RAY SYSTEM AND METHOD”, the entire contentsof which are incorporated herein by reference.

1. A breast tomosynthesis system comprising: an x-ray source and anx-ray imaging receptor having first and second lateral sides; a receptorhousing concealing the receptor, said housing having a generally flatupper surface having lateral sides and configured to support a patient'sbreast between the source and the receptor, with the breast extendingaway from the patient in a direction generally parallel to said lateralsides of the upper surface of the housing; said source being supportedfor rotational movement relative to the upper surface of the receptorhousing from a position closer to one of said lateral sides of the uppersurface of the receptor housing to a position closer to the otherlateral side of the upper surface of the receptor housing; and saidreceptor being supported for movement relative to the upper surface ofthe receptor housing during said rotational movement of the source; acompression paddle and a biasing mechanism coupled with the compressionpaddle and configured to cause a front end of the compression paddle totilt against a bias force relative to the receptor housing as apatient's breast is being compressed between the paddle and the uppersurface of the receptor housing in first selected imaging modes suchthat the front end of the paddle is further from the upper surface ofthe receptor housing than a rear side of the paddle; wherein saidmovement of the receptor during the rotational movement of the sourcecomprises moving the receptor about a receptor axis that is intermediatethe lateral extent of the receptor and generally parallel to the lateralsides of the receptor to move one of the lateral sides of the receptortoward said upper surface.
 2. A breast tomosynthesis system comprising:an x-ray source and an x-ray imaging receptor having first and secondlateral sides; a receptor housing concealing the receptor, said housinghaving a generally flat upper surface having lateral sides andconfigured to support a patient's breast between the source and thereceptor, with the breast extending away from the patient in a directiongenerally parallel to said lateral sides of the upper surface of thehousing; said source being supported for rotational movement relative tothe upper surface of the receptor housing from a position closer to oneof said lateral sides of the upper surface of the receptor housing to aposition closer to the other lateral side of the upper surface of thereceptor housing; and said receptor being supported for movementrelative to the upper surface of the receptor housing during saidrotational movement of the source; wherein said movement of the receptorduring the rotational movement of the source comprises moving thereceptor about a receptor axis that is intermediate the lateral extentof the receptor and generally parallel to the lateral sides of thereceptor to move one of the lateral sides of the receptor toward saidupper surface of the housing while the other lateral side of thereceptor is moving away from said upper surface of the housing; acompression paddle mounted between the source and the upper surface ofthe receptor housing; and a lateral motion mechanism coupled with thecompression paddle and configured to selectively move the compressionpaddle toward and into an offset position relative to the lateral sidesof the upper surface of the receptor housing.
 3. A breast tomosynthesissystem comprising: an x-ray source and an x-ray imaging receptor havingfirst and second lateral sides; a receptor housing concealing thereceptor, said housing having a generally flat upper surface havinglateral sides and configured to support a patient's breast between thesource and the receptor, with the breast extending away from the patientin a direction generally parallel to said lateral sides of the uppersurface of the housing: said source being supported for rotationalmovement relative to the upper surface of the receptor housing from aposition closer to one of said lateral sides of the upper surface of thereceptor housing to a position closer to the other lateral side of theupper surface of the receptor housing; and said receptor being supportedfor movement relative to the upper surface of the receptor housingduring said rotational movement of the source; wherein said movement ofthe receptor during the rotational movement of the source comprisesmoving the receptor about a receptor axis that is intermediate thelateral extent of the receptor and generally parallel to the lateralsides of the receptor to move one of the lateral sides of the receptortoward said upper surface of the housing while the other lateral side ofthe receptor is moving away from said upper surface of the housing; afirst support arm supporting said x-ray source; a second support armsupporting said receptor housing and receptor; and a locking mechanismselectively locking the first and second support arms and thecompression paddle for rotation of the source, receptor and receptorhousing, and compression paddle as a unit and unlocking the first andsecond support arms for rotation of at least one relative to the other.4. The breast tomosynthesis system of claim 1 in which the compressionpaddle is locked against tilting in second selected imaging modes. 5.The tomosynthesis system of claim 1 further comprising: a normal motionmechanism coupled with the compression paddle and configured to move thecompression paddle toward and away from the upper surface of thereceptor housing.
 6. The tomosynthesis system of claim 5 furthercomprising: a motor selectively driving the paddle in a lateral movementthereof.
 7. The tomosynthesis system of claim 5 further comprising: ashifting mechanism causing automatic lateral movement of the compressionpaddle toward one of the lateral sides of the upper surface of thereceptor housing depending on a view to be acquired.
 8. A tomosynthesissystem comprising: an x-ray source and an x-ray imaging receptor havingfirst and second lateral sides; a receptor housing concealing thereceptor, said housing having a generally flat upper surface havinglateral sides and configured to support a patient's breast between thesource and the receptor, with the breast extending away from the patientin a direction generally parallel to said lateral sides of the uppersurface of the housing; said source being supported for rotationalmovement relative to the upper surface of the receptor housing from aposition closer to one of said lateral sides of the upper surface of thereceptor housing to a position closer to the other lateral side of theupper surface of the receptor housing; and said receptor being supportedfor movement relative to the upper surface of the receptor housingduring said rotational movement of the source; wherein said movement ofthe receptor during the rotational movement of the source comprisesmoving the receptor about a receptor axis that is intermediate thelateral extent of the receptor and generally parallel to the lateralsides of the receptor to move one of the lateral sides of the receptortoward said upper surface of the housing while the other lateral side ofthe receptor is moving away from said upper surface of the housing; apaddle support mounted for movement toward and away from the receptorhousing; and a paddle holding mechanism forming a part of the paddlesupport and configured to selectively hold and release differentlyshaped or sized compression paddles for movement therewith toward andaway from the receptor housing and for lateral movement relative to thepaddle support toward one or the other of the lateral sides of the uppersurface of the receptor housing.
 9. A breast tomosynthesis systemcomprising: an x-ray source and an x-ray imaging receptor having firstand second lateral sides; a receptor housing concealing the receptor,said housing having a generally flat upper surface having lateral sidesand configured to support a patient's breast between the source and thereceptor, with the breast extending away from the patient in a directiongenerally parallel to said lateral sides of the upper surface of thehousing; said source being supported for rotational movement relative tothe upper surface of the receptor housing from a position closer to oneof said lateral sides of the upper surface of the receptor housing to aposition closer to the other lateral side of the upper surface of thereceptor housing; and said receptor being supported for movementrelative to the upper surface of the receptor housing during saidrotational movement of the source; wherein said movement of the receptorduring the rotational movement of the source comprises moving thereceptor about a receptor axis that is intermediate the lateral extentof the receptor and generally parallel to the lateral sides of thereceptor to move one of the lateral sides of the receptor toward saidupper surface of the housing while the other lateral side of thereceptor is moving away from said upper surface of the housing; a firstsupport arm supporting the source; a second support arm supporting acompression paddle and the receptor housing; said first and secondsupport arms being mounted for selective rotation of at least onerelative to the other in one mode of operation of said system and forjoint rotation in another mode.
 10. The breast tomosynthesis system ofclaim 9 in which the selective rotation of at least one of the first andsecond support arms relative to the other is about a common axis. 11.The breast tomosynthesis system of claim 1 further comprising: a needlebiopsy stage secured to one of said arms and located between the sourceand the receptor housing.
 12. The breast tomosynthesis system of claim 1further comprising: a computerized work station coupled with the sourceand receptor to command the operation mode thereof and to process imagedata generated by the receptor.
 13. The breast tomosynthesis system ofclaim 1 in which said receptor housing encloses the front, the sides,the top and the bottom of the x-ray imaging receptor.
 14. A breasttomosynthesis method comprising: selectively locking to each other afirst support arm supporting a source of an x-ray beam and a second armsupporting an x-ray imaging receptor concealed in a receptor housingthat has an upper surface located between the source and the receptorand further has lateral sides, for rotation of the source, receptor andhousing as a unit about a source rotation axis, and unlocking the firstand second arm from each other for individual rotation of at least oneof the arms relative to the other while a patient's breast is pressedagainst and supported by said upper surface of the receptor housing;selectively moving the imaging receptor about a receptor rotation axisrelative to the second support arm and relative to said upper surface ofthe receptor housing while rotating the first support arm about saidsource rotation axis; wherein said receptor rotation axis isintermediate the lateral extent of the receptor and parallel to thelateral sides of the receptor housing, and wherein said moving of thereceptor comprises moving one lateral end of the receptor toward theupper surface of the receptor housing while an opposite lateral end ofthe receptor is moving away from the upper surface of the receptorhousing; acquiring projection x-ray image data from the receptor whilerotating the source support arm and moving the image receptor; andcomputer-processing the image data into images for display andselectively displaying at least some of the images.
 15. The breasttomosynthesis method of claim 14 further comprising synchronizing therotational movement of the source and said movement of the receptor. 16.The breast tomosynthesis method of claim 14 further comprisingcompressing the patient's breast between a compression paddle and saidupper surface of the receptor housing.
 17. The breast tomosynthesismethod of claim 14 further comprising selectively positioning ananti-scatter grid in a first position between the receptor and the uppersurface of a receptor housing and removing the grid from said firstposition.
 18. The breast tomosynthesis method of claim 17 furthercomprising driving said grid to and out of said first position with amotor.
 19. The breast tomosynthesis method of claim 14 furthercomprising providing a compression paddle mounted between the receptorhousing and the source for tilting against a bias relative to the uppersurface of the receptor housing in first selected imaging modes.
 20. Thebreast tomosynthesis method of claim 19 further comprising locking thecompression paddle against tilting in second selected imaging modes. 21.The tomosynthesis method of claim 14 further comprising mounting acompression paddle for movement toward the receptor to compress apatient's breast and for lateral movement relative to the receptor tooffset the paddle relative to the lateral sides of the upper surface ofthe receptor housing.
 22. The tomosynthesis method of claim 21 furthercomprising selectively driving the paddle in said lateral movementthereof with a motor.
 23. The tomosynthesis method of claim 21 furthercomprising providing a shifting mechanism causing automatic lateralmovement of the compression paddle depending on a view to be acquired.24. The tomosynthesis method of claim 14 further comprising providing apaddle support mounted for movement toward and away from the receptorand a compression paddle removably mounted to the paddle support formovement therewith toward and away from the receptor and for lateralmovement relative to the paddle support.
 25. The breast tomosynthesismethod of claim 14 including mounting said first and second arms forrotation relative to the other about a common axis.
 26. The breasttomosynthesis method of claim 14 further comprising mounting a needlebiopsy stage between the source and the receptor.
 27. The breasttomosynthesis method of claim 14 further comprising providing acomputerized work station coupled with the source and receptor tocommand the operation mode thereof and to process image data generatedby the receptor.